Convert GN visibility variables to lists.

content/browser/devtools/BUILD.gn

Index: content/browser/devtools/BUILD.gn
diff --git a/content/browser/devtools/BUILD.gn b/content/browser/devtools/BUILD.gn
index 89e93b96d905f2fae755e0a8a2837ca38d002a0d..bc2b60d92434e6c06a1261299c54e2abfc6928fe 100644
--- a/content/browser/devtools/BUILD.gn
+++ b/content/browser/devtools/BUILD.gn
@@ -37,7 +37,7 @@ grit("devtools_resources") {
 }
 
 action("gen_devtools_protocol_constants") {
-  visibility = ":devtools_protocol_constants"
+  visibility = [ ":devtools_protocol_constants" ]
 
   script = "//content/public/browser/devtools_protocol_constants_generator.py"
 
@@ -57,6 +57,6 @@ action("gen_devtools_protocol_constants") {
 }
 
 source_set("devtools_protocol_constants") {
-  visibility = ":resources"
+  visibility = [ ":resources" ]
   sources = get_target_outputs(":gen_devtools_protocol_constants")
 }